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Crews Work to Save Yosemite Sequoias, Tree That Usually Thrives With Fire’s Help

August 30, 2013 at 12:00 AM EDT
Sequoias are among Earth's oldest and most massive trees. But a wildfire raging near California's Yosemite National Park has put some of their unique groves at risk. Kwame Holman reports on the effort by nearly 4,000 firefighters to contain the blaze and protect these environmental treasures.
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JEFFREY BROWN: Firefighters in California reported more progress today in the two-week battle against a huge wildfire near Yosemite National Park.

A NewsHour team has been covering one of their top priorities: protecting an ancient grove of giant sequoias in the park.

Kwame Holman narrates this report.

MAN: Well, we’re almost to the big tree.

KWAME HOLMAN: Even as wildfires raged miles away on the other end of Yosemite, a steady stream of visitors this week hiked up a scenic trail to see one of the park’s biggest attractions, the giant sequoias.

These massive trees, which are unique to California’s Sierra Nevada Mountains, are among the oldest living organisms on Earth. The grandest in Yosemite’s Mariposa Grove is the so-called Grizzly Giant, estimated to be 1,800 years old, and it’s no stranger to fire.

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Many sequoias here bear huge black scars from natural wildfires that have burned through these forests for thousands of years. But now an unprecedented fire, the largest in Sierra history, is threatening two of Yosemite’s three giant sequoia groves.

The Rim fire, which has consumed more than 300 square miles since it began on August 17, is burning near the Tuolumne and Merced groves on the western boundary of the park. More than 4,000 firefighters from around the country have been battling the intense blaze. Many work out of the incident command center near the fire’s front lines just outside Yosemite.

It’s a sprawling temporary city where crews can get grub and rest between shifts. And this is where officials have been closely monitoring the fire’s advance toward the sequoias.

TOM MEDEMA, National Park Service: The fire is still about five miles away from the groves. It’s getting a little bit closer every day.

KWAME HOLMAN: Tom Medema speaks about the fire for the National Park Service, which has taken steps to try to protect the trees.

TOM MEDEMA: We have done work there setting out sprinklers where we can moisten fuels, so that they are not as receptive to those — the embers that are coming in. We have got firebreaks that are built in. And then there’s also in the Merced grove a really important historic structure, one of the first ranger cabins in the park. And we have wrapped that in a fire-retardant material to protect that as well.

KWAME HOLMAN: At the park’s Mariposa Grove, a safe distance away from the fire, visitors expressed concern for the threatened trees.

WOMAN: They have been here for so long. And they are just a part of the state and a part of America and who we are. To lose them would be just awful.

DEAN SHENK, Yosemite National Park: What’s amazing is that one of these can sprout from one of these. These are each sequoia seeds.

KWAME HOLMAN: Dean Shenk has been a ranger in Yosemite for 40 years. He educates the public about the park’s iconic giants. Since the Rim Fire began, Shenk has answered a lot of questions about how the sequoias cope with fire.

DEAN SHENK: Fire is part of the natural balance of things. Like rain, you want to have a little bit of rain, but you don’t want to have too much. This is too much fire.

KWAME HOLMAN: Shenk says the mighty trees have their own defense mechanisms against fire, including a natural flame retardant in their thick bark, which do a pretty good job of defending them from most fires.

DEAN SHENK: It’s rare to find a large sequoia tree that doesn’t have a major fire scar. At ground level, sequoia bark is two-feet thick, sometimes even a little thicker, but as you get up the tree a short distance, maybe 40 feet off the ground, the bark is surprisingly thin, just a few inches.

KWAME HOLMAN: At a nearby stand of young sequoias, Shenk explained how a prescribed burn, a low-intensity fire set and controlled by park staff, standard practice in the park for 40 years, actually helps the trees reproduce.

DEAN SHENK: We’re looking at cluster of giant sequoias that are about 14 years old. And all of them owe their existence to a prescribed burn that we had here about 15 years ago.

We burned this area five years ago with a prescribed burn and again about 15 years ago as well. The natural forest debris that was on top of the forest floor was burned away, recycling nutrients, allowing for lots of sunshine, to where the seeds that were dispersed shortly after the fire were able to take hold. And so we have a great rejuvenation pocket right here in the midst of the Mariposa Grove.

KWAME HOLMAN: But while the giant sequoias in Yosemite Park have been enduring fire for centuries, even thriving because of it, those fighting the Rim fire say this blaze poses a threat to the trees. It’s one of the hottest and fastest moving fires in recent times.

TOM MEDEMA: In this type of fire and the fires that you see, the flames that you see in the news are these crowning flames that are going up into the tops or the crown of the tree and carrying from treetop to treetop.

And it is much more devastating, because it is burning all the green growth, as opposed to just burning the dead stuff on the ground. And so we need to take measures to try and knock this down before it can get into the crowns of the giant sequoias.

JOHN WALLACE, U.S. Fish and Wildlife Service: You can see here behind us here these trees, this brush was just totally consumed in the flames.

KWAME HOLMAN: John Wallace is a forest fuels specialist with the U.S. Fish and Wildlife Service. He says the intensity of the Rim fire is due, in part, to years of forest management policies, largely in land outside the park, which suppressed naturally occurring wildfires.

JOHN WALLACE: Everything out here, when it falls on the ground, becomes a fuel. Now, years and years of suppression have let fuels build up to a level that’s unnatural. And so in the last 15 years or so, the Department of Interior agencies have really gone in — and the Forest Service — have really started trying to manage those fuel loads and introduced prescribed fire back into the landscape to help get fuels down to a more natural level. And this is one of that areas that they haven’t gotten to yet.

KWAME HOLMAN: Wallace says that while the Rim fire is a particularly devastating wildfire, such mega-fires are becoming the norm, rather than the exception.

JOHN WALLACE: These fires are just becoming more and more common now.

I mean, since 2000, we have had all these 500,000-acre, 600,000-acre fires, these mega-fires. Before 2000, a 100,000-acre fire was huge. But things have been warming up, drying out. And then we have got these high fuel loads in a lot of places. And that’s contributing to these bigger, more intense fires.

KWAME HOLMAN: Officials say they are starting to get a handle on fire, which is about 30 percent contained, and they hope to have it fully contained by the end of September. Until then, crews stationed near the giant sequoias are standing by, ready to put up whatever fight they can, if needed, to save these national treasures.

JEFFREY BROWN: On our Science page, you can read more about how a century of fire suppression has made fires worse for the legendary giant sequoias. And take a look at behind-the-scene photos from our reporting.